NSW Seasonal Conditions Summary May 2015

Highlights

  • Excellent rainfall over most cropping areas allowed timely sowing of winter crops. Rainfall was above average over 79 per cent of NSW. Heavy rainfall from the Illawarra to the north coast has caused flooding and some crop damage.
  • Wetter than normal conditions are likely across most of NSW between May and July. Daytime temperatures are likely to be cooler in the west and areas of central and north western NSW. There is a near-equal chance of warmer or cooler than normal temperatures over the remainder of NSW. Overnight temperatures are likely to be warmer.
  • During May, there is a near-equal chance of drier or wetter than normal conditions across NSW, with warmer daytime temperatures in the north west and some central areas, and a near-equal chance of warmer or cooler than normal temperatures for the rest of NSW. Overnight temperatures are likely to be warmer in the north.
  • An El Niño event has commenced and may continue into spring. Such events are associated with a likelihood of reduced winter/spring rainfall, higher daytime temperatures and an increased risk of frost.
  • The current seasonal rainfall outlook remains positive due to warm sea surface temperatures to the north west and north east of Australia.
  • Topsoil moisture levels improved over eastern and central NSW.  Subsoil moisture levels were generally stable, but improved across the northern slopes. Continued poor run off has limited farm water supplies in many areas.
  • Pasture growth improved over most of NSW, but has been slow in some areas and has been affected by waterlogging over areas of the coast.
  • Forage crops have responded well. Further sowings occurred in early April. Sowings of early maturing winter crops have commenced. Some supplementary feeding of stock is occurring. Summer crop yields have generally been good.
  • Resources to assist in management for areas suffering poor rainfall and growth are available at Managing drought.

Overview

Rainfall during April was above average across 79 per cent of NSW and average across 11 per cent. Above average rainfall occurred across most of the cropping areas. Across some areas of the Hunter valley and Sydney basin, rainfall was the highest on record.

While areas of the north west received near average rainfall, it was insufficient to replenish subsoil moisture reserves.

Pasture growth improved across most of NSW in response to the good April rainfall, but has been slow in some areas including the west, central west and tablelands. Growth remained relatively stable across the mid-north to north coast, but was affected by heavy rainfall, waterlogging and flooding.

Relative to historical records, growth improved from below average to average or above across much of western and central NSW. Relative growth improved to above average across much of the northern slopes, the west of the northern tablelands and areas of the upper Hunter valley, central west, central and southern tablelands. Relative growth remained near average along the coast and the east of the northern tablelands, but remained low across north western NSW. Supplementary feeding is continuing in this area and areas of western NSW.

Biomass levels improved slightly, particularly across the northern slopes and the tablelands. Biomass remained low across much of central and western NSW and along the coast. Relative to historical records, biomass was well below average across the north west (west of the Newell Highway), below average in the western Riverina and average or above across the tablelands and areas of the far west. Relative biomass was high over the northern slopes, the west of the northern tablelands and areas of the central west, central tablelands and upper Hunter valley.

The April rainfall stimulated sowings of dual purpose and later maturing winter crops across most cropping areas, switching to earlier maturing varieties in May. Early sown forage crops have responded well. Rainfall in the north west (west of the Newell Highway) has generally been insufficient for winter crop sowings, although some dry sowing has occurred.

Cotton harvesting was delayed by the April rainfall. Yields of summer crops have generally been good.

Flooding has affected pastures and forage crops in areas of the Sydney basin, Hunter valley and mid-north coast. Cane and soybean crops, macadamias and bananas have been affected by heavy rainfall on the north coast.

Topsoil moisture levels improved across eastern and central NSW, and were above average across most of these areas. Subsoil moisture levels remained relatively stable, but improved across the northern slopes.Streamflow analysis over the last year indicated an improvement in run off across areas of the coast, but remained low across much of central and north western NSW. Some areas have received run off but others very little.

NSW Seasonal Conditions Report – May 2015

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Seasonal outlook

Although an El Niño event is commencing, the current seasonal rainfall outlook is generally positive. This is as a result of warmer than normal sea surface temperatures to the north west and north east of Australia.

Wetter than normal conditions are likely across most of NSW between May and July, with the probabilities increasing towards the west. There is a near equal chance of drier or wetter than normal conditions in the far south east.

Cooler than normal daytime temperatures are likely between May and July over the northern and central areas of the far west, and areas of the central west and north west of NSW. There is a near equal chance of cooler or warmer than normal daytime temperatures for most of eastern and southern NSW. Warmer than normal daytime temperatures are likely in the far south east.

Warmer than normal overnight temperatures are likely across NSW during the May to July period.

During May, there is a near-equal chance of drier or wetter than normal conditions across NSW. Daytime temperatures are likely to be warmer than normal in the north west and areas of central NSW and the far north east. For most of eastern, central and southern NSW there is a near-equal chance of cooler or warmer than normal temperatures. Overnight temperatures are likely to be warmer than normal in the north and west of NSW. There is a near-equal chance of cooler or warmer than normal overnight temperatures in the south and areas of the mid-north coast and the south of the northern tablelands.

The pasture growth outlook for May to July suggests above average growth is possible over the period for the western half of tablelands, the slopes and much of the Riverina and southern NSW. Average growth is possible across areas of the north west and much of the coast, but below average growth is possible in the south east. Skill levels are moderate to high in these areas, but the outlook for the remainder of the State has low skill. The outlook is based a negative SOI in March/April, and a moderate probability of above average rainfall across NSW during May to July.

El Niño Southern Oscillation (ENSO)

The Pacific Ocean is in the early stages of an El Niño event. The Bureau of Meteorology's ENSO tracker status is now at 'El Niño'.

Climate models surveyed by the Bureau suggest central Pacific (NINO3.4 region) sea surface temperatures remaining at or above the Bureau's El Niño thresholds through winter and into spring.

The NOAA Climate Prediction Centre and International Research Institute for Climate and Society in the USA have indicated that (based on their thresholds and indicators) a weak El Niño event commenced in February, has about a 90 per cent chance of continuing through winter and is likely to reach moderate strength.

An El Niño event is generally associated with below-average rainfall across NSW (particularly inland NSW) during winter and spring, above average daytime temperatures, lower than average streamflow and an increased risk of frost.

Warm sea surface temperatures anomalies extend across the majority of the equatorial Pacific, and continued to strengthen during April, particularly in the east. All NINO indices (to 10 May) are close to or more than 1°C above normal, with the NINO 2 index (far east) more than 2°C above normal.

Sub-surface warm temperature anomalies increased in the western-central Pacific during the last four months and moved eastwards, warming the sea surface. Warm sub-surface anomalies now extend across the central and eastern equatorial Pacific, and strengthened in the east. A small cool anomaly formed at depth in the west over recent months.

The SOI remained in the neutral range between mid-April to early May, then fell back to negative once more. The SOI was -11.4 as at 11 May. Westerly anomalies in the trade winds extend across the western equatorial Pacific, and the trade winds have been consistent weaker than average. Cloud at the junction of the equator and the International Date Line has been above average since early March. These indicators are consistent with coupling between the atmosphere and ocean.

Climatic outlook summary

NSW Seasonal Outlook Current outlook Previous outlook
Quarterly Rainfall

Wetter

Wetter

Near neutral – neutral
(central to north coast)

Quarterly Maximum Temperature

Cooler
(western and areas of central NSW)

Near neutral
(southern, eastern, most of central NSW)

Warmer
(far south east)

Warmer
(eastern and eastern-central NSW)

Near neutral
(western, northern and central NSW)

Quarterly Minimum Temperature

Warmer

Warmer

El Niño Southern Oscillation (ENSO)
ENSO (overall) El Niño Neutral – possible El Niño developing in winter (NOAA - weak El Niño)
BoM ENSO Tracker Status El Niño El Niño Alert
SOI Negative Neutral (negative)
Pacific Ocean (NINO3.4)

Warm
(Above El Niño thresholds)

Warm
(currently neutral, but near El Niño threshold and warming)

Indian Ocean (IOD) Neutral Neutral 
Southern Annular Mode (SAM/AAO) Near neutral – weakly negative Near neutral - weakly positive

Rainfall and temperature

During April, rainfall across the state ranged from 8-535 mm, and was above average across most of the state. The lowest rainfall fell across areas of north western and western NSW, and ranged from 8-25 mm. Areas of low rainfall occurred near Bourke and Fowlers Gap. Extremely high rainfall occurred as a result of East Coast Lows, particularly affecting the Hunter valley, Sydney basin and Illawarra.

Daytime temperatures were 1.0°C below normal across NSW during April. The central areas, south east and far west had temperatures of down to 2.0°C below normal. Overnight temperatures were 0.4°C above normal across NSW. Overnight temperatures were generally cooler in the west and north east and near normal across central and most of eastern NSW. Temperatures were above normal in areas of the central west and Riverina.

Relative rainfall

Relative to historical records, rainfall during April was above average to extremely high across most of the State (79 per cent) except the north coast and areas of the north west, far west and south. In these areas, rainfall was generally average.

Areas of the far south west, northern tablelands and slopes, the Hunter valley central tablelands, Sydney basin, Illawarra and far south east received extremely high relative rainfall. Areas of the Sydney Basin and Hunter valley received their highest April rainfall on record, as a result of the East Coast Low.

Quarterly relative rainfall was average over 79 per cent of the State, but was well below average across an area between Coonamble, Walgett, Lightning Ridge, Goodooga and Weilmoringle. Other areas of below average rainfall occurred near Nyngan, between Cobar and Ivanhoe, adjacent to the Liverpool Plains and south of Deniliquin. Above average rainfall for the period occurred primarily across the Sydney basin, southern Hunter valley, to the north west of Glen Innes and in the far south east.

Half yearly relative rainfall was average across most of western and central NSW. It was above average over much of the coast and tablelands, and in the far west. Below average relative rainfall for the period occurred in areas of the north west, the Liverpool Plains and an area of the far south west south of Balranald.

Soil moisture

Modelled topsoil moisture levels increased across eastern and central NSW during April.

Relative to historical records, topsoil moisture was generally above average across the central and eastern areas of the State, with the exception of the north coast. The north coast, western Riverina and much of the far west had average topsoil moisture. Patches of low topsoil moisture occurred in the far north west.

Modelled subsoil moisture levels were generally stable during April, but remained low in areas of the north and west.Relative to historical records, subsoil moisture remained below average across much of the north west and central areas of the northern tablelands, Liverpool plains, the south of the central tablelands and the south and west of the Riverina. Relative subsoil moisture was extremely low across areas of the north west.

Streamflow

Despite the April rainfall, many inland areas have experienced very little run off. Farm water supplies are low in many areas, with some areas critically low.Streamflow analysis over the last year indicated run off over much of northern and central NSW, the tablelands, the upper Hunter valley and the Riverina remained well below average. Run off was average or better over much of the coast.

The Bureau of Meteorology's streamflow forecast indicates low streamflows were recorded during May to July is likely at inland locations with below-average soil moisture and low to median flows elsewhere. High flows are most likely in coastal areas affected by the East Coast Lows. High April streamflows were recorded in these areas.

Relative pasture growth and biomass

Relative to historical records, AussieGRASS modelled pasture growth improved across most of western, central and south eastern NSW during April. Across the central to north coast and the eastern fall, growth remained near average. Relative growth improved to well above average or better across much of the northern slopes, the east of the northern plains, the central tablelands, central west slopes, southern tablelands and areas of the south. Relative growth remained low in areas of the north west, west of the Newell Highway.

Relative growth for April was below average over just 6 per cent of NSW, average over 44 per cent and above average over 26 per cent. However, there were large areas of missing data, particularly in the west.

Other pasture growth models indicated well above average growth for temperate pastures across most of NSW, with the exception of the coast, eastern fall, north west and areas of the far west and south west. For tropical pasture species, the best growth occurred along the mid-north to north coast.

Over the three months to April, relative growth was average to above average across much of the tablelands and far west of NSW and areas of the south. It was below average across areas of the north west, the south east, the north western Riverina and the north east of western NSW. The remainder of central and coastal NSW had average growth.

Relative biomass levels improved across much of the central and northern the tablelands, northern slopes. south, central west and eastern Riverina. Relative biomass remained low across the north west and much of the western Riverina. About 23 per cent of NSW had below average relative biomass levels, and 77 per cent average or better relative biomass levels.

Figure 1: Relative monthly topsoil moisture

Figure 2: Relative quarterly pasture growth

More information

For more information, contact the NSW Department of Primary Industries on 02 6391 3100 or Local Land Services on 1300 795 299.

Acknowledgments

Information used in this report was sourced from the Bureau of Meteorology, CSIRO, Queensland Department of Science, Information Technology and Innovation, NSW Local Land Services, the US National Oceanic and Atmospheric Administration, the International Research Institute for Climate and Society (Columbia University) and NSW Department of Primary Industries.

External links

Disclaimer

The seasonal outlooks presented in this report are obtained from the Australian Bureau of Meteorology and other sources. These outlooks are general statements about the likelihood (chance) of (for example) exceeding the median rainfall or minimum or maximum temperatures. Such probability outlooks should not be used as categorical or definitive forecasts, but should be regarded as tools to assist in risk management and decision making. Changes in seasonal outlooks may have occurred since this report was released. Outlook information was up to date as at 7 May 2015.

Recognising that some of the information in this document is provided by third parties, the State of New South Wales, the author and the publisher take no responsibility for the accuracy, currency, reliability and correctness of any information included in the document provided by third parties.

The information contained in this publication is based on knowledge and understanding at the time of writing (7 May 2015). However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information with the appropriate officer of the Department of Primary Industries, Local Land Services or the user's independent adviser.